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SQLite

SQLite. Found Things. Record a thing (e.g., audio, picture, text, video, web link, etc.) at a location When someone is near the location, perhaps play the thing. Allow things that are played to be selected in a sophisticate way Include various information about the things

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SQLite

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  1. SQLite

  2. Found Things • Record a thing (e.g., audio, picture, text, video, web link, etc.) at a location • When someone is near the location, perhaps play the thing. • Allow things that are played to be selected in a sophisticate way • Include various information about the things • Cache things and get things from the web

  3. Things database Look in database and get thing from nearby and that matched other criteria For now, we will just use near by lat and long

  4. SQLite • SQLite is a scaled down version of SQL • Data is in tables with rows and columns • Each row is a data entry. • SQL allows data to be stored and retrieved • Basic things (see http://www.w3schools.com/sql/default.asp • Create database • Create table in the database • Insert data into the table • Get data from table (or tables), via query • There’s other stuff, but this is enough for us

  5. Create database and table • SQLiteDatabasemyDatabase; • myDatabase = openOrCreateDatabase( “/mnt/sdcard/things.db", SQLiteDatabase.CREATE_IF_NECESSARY, null); • Makes a database called things.db • If no path, then db is in /data/data/<appname>/databases • here we use a specific path so we can examine the db at the command line • Is database already exists, it does not make it • Make table • Must specify the column name and type (e.g., integer) • Also, there must be a primary column (a key) such that each entry in this column is unique • One way to do this is to include a column that is an integer that autoincrements If “IF NOT EXIST” is missing, then this will crash if the table already exists Name of table myDatabase.execSQL("CREATE TABLE IF NOT EXISTS things" + "( id INTEGER PRIMARY KEY AUTOINCREMENT," + " type VARCHAR(40), " + " filename VARCHAR(40), " + " lat INTEGER, " + " long INTEGER);"); Key is named id and is integer Type is audio, pic, tex, etc. Filename of the thing Location of the thing

  6. Try it • Make function createDatabase • Call createDatabase from onCreate • Run adb • Change to the databases directory • ls • Run sqlite3 things.db “.dump”

  7. Add data Id of entry Name of table long newId = myDatabase.insert("things", null, values); Set of pairs (column name, data for that column) ContentValues values = new ContentValues(); values.put("type", "audio"); values.put("filename", "1.mp4"); values.put("lat","75001200"); values.put("long","36000000");

  8. Try it • Make function insertData() ContentValues values = new ContentValues(); values.put("type", "audio"); values.put("filename", "1.mp4"); values.put("lat","75001200"); values.put("long","36000000"); long newId = myDatabase.insert("things", null, values); Log.d(“SQLPlay”,”insert returned id “+newId); • Run • adb sqllite3 things.db “.dump”

  9. Add three buttons • Record • Stop • Play • Allow record audio, location, internet, camera

  10. Next filename • We will save the recorded data with name id.mp4, where id is the id from the database • So, to determine the filename, we need to get the next id • Or, insert a partial row, get the id and update the row

  11. ContentValuesvalues = new ContentValues(); values.put("type", "audio"); values.put("lat“, 36000000); values.put("long“,74000000); long newId = myDatabase.insert("things", null, values); Log.d(“SQLPlay","newId="+newId); Make a new column with the filename empty (null) Make file name String filename = newId+".mp4"; ContentValues values2 = new ContentValues(); values2.put("filename", Long.toString(newId)+".mp4"); String wheres[] = new String[1]; wheres[0] = Long.toString(newId); myDatabase.update("things", values2, "id=?", wheres); Make filename column (value pairs like insert) update

  12. location • From previous lectures on location • Add class attribtues • LocationManagerlocationManager; • String provider; • Make setUpLocation and call from onCreate, after createDatabase public void setUpLocation() { Criteria criteria = new Criteria(); criteria.setAccuracy(Criteria.ACCURACY_FINE); criteria.setPowerRequirement(Criteria.NO_REQUIREMENT); locationManager = (LocationManager)getSystemService(Context.LOCATION_SERVICE); provider = locationManager.getBestProvider(criteria, true); Location location = locationManager.getLastKnownLocation(provider); String locInfo = String.format("Initial loc = (%f, %f) @ (%f meters up)", location.getLatitude(), location.getLongitude(), location.getAltitude() ); Log.d("SQLPlay","starting loc: "+locInfo); } Get location

  13. Location when not moving/indoors • Get gps lock since last reboot. That way, .getLastKnownLocation doesn’t crash • Add a random number to location Location location = locationManager.getLastKnownLocation(provider); Random generator = new Random(); int random1 = generator.nextInt( 1000000 ); int random2 = generator.nextInt( 1000000 ); int latitude = (int)(location.getLatitude()*1E6+random1); int longitude = (int)(location.getLongitude()*1E6+random2); • Put this into getNextfileNamefunction • rmthings.db • Run and make a few files. Dump database

  14. Record sound • From previous project, cut record sound and paste into recordSound function • Cut and paste stopRecording into stopRecordingButton.onClick • Make buttons nice • Run on device • Make a few entries • adb -d pull /data/data/com.SQLPlay/files c:\audio • adb -d pull /data/data/com.SQLPlay/databases c:\audio

  15. Play sound • Get location (done) • Get database entry that is nearest to current location • Android query • SQL SELECT

  16. public Cursor query (String table, String[] columns, String selection, String[] selectionArgs, String groupBy, String having, String orderBy, String limit) • Table = “things” • Columns: array of the columns to be returned • E.g., null, returns all columns • E.g., String columns[] = “filename”; returns the filename • {selection selectionArgs} is also know as WHERE (in SQL, one types …. WHERE ~ {selection selectionArgs} • E.g., selection = “type=?”; String selectionArgs[] = {“audio”} • E.g., selection = “lat<?”; String selectionArgs[] = {“90000000”} • E.g., selection = “lat<? AND type=?”; String selectionArgs[] = {“90000000”, “audio”} • Groupby and having are for grouping (we set as null) • Orderby is to order the replies (we set as null) • Limit controls how many to return (we set as null) • If orderBy is used, then limit can be used to get the first or first few • E.g., orderBy = “cost”; limit = “1”; returns the row with the highest cost Cursor c = myDatabase.query (“things”, null , null, null, null, null, null, null);

  17. cursor • Cursor is used to get the results, which might be emtpyor have several rows, where each row has one or more columns • You can scroll through the cursor • Also, you should close the cursor when done • Perhaps use startManagingCursor(c); c.moveToFirst(); while (c.isAfterLast() == false) { String row = new String(); for (inti=0; i<c.getColumnCount(); i++) row += c.getString(i) + " "; Log.d("SQLPlay",row); c.moveToNext(); } c.close();

  18. Try it • Make function playAudio and call this function from playButton.onClick • Make function, getfilename • In playAudio, call getFilename • In getFilename, put Cursor c = myDatabase.query (“things”, null , null, null, null, null, null, null); c.moveToFirst(); while (c.isAfterLast() == false) { String row = new String(); for (inti=0; i<c.getColumnCount(); i++) row += c.getString(i) + " "; Log.d("SQLPlay",row); c.moveToNext(); } c.close(); Run, select play, and look at log.

  19. Try other selections String selection = “lat<?” String selectionArgs[] = {“90000000”}; String selection = “lat BETWEEN ? AND ?” String selectionArgs[] = {“0”, “90000000”}; String selection = “lat IN ” String selectionArgs[] = {“somevalue”}; Exact match (maybe somevalue can be a set?) String columns[] = “max(lat)” Everything else null String columns[] = “min(abs(lat-70000000))” Everything else null

  20. nearest • But how to get a nearest point? • I don’t think it is possible with this type of query • rawQuery • Same as SQLite queries. • Android’s query is easy, but very limited. rawQuery gives the full power of SQLite • If you know SQL, then you may as well use rawQuery

  21. SQL SELECT • SELECT column_name(s) • FROM table_name • WHERE column_name operator value • SELECT * FROM things WHERE lat < 90000000 • Try in sqlite3 • In shell, # sqlite3 things.db “SELECT * from things” ….

  22. Smallest lat • SELECT * FROM things WHERE lat in (SELECT min(lat) ) • Nearest lat to 4000000 • SELECT * FROM things WHERE abs(lat-40000000) in (SELECT min(abs(lat-40000000) ) ); • Nearest to La, Lo • SELECT * FROM things WHERE abs(lat - La)+abs(long - Lo) in (SELECT min(abs(lat - La)+abs(long - Lo) ) ); • Don’t forget spaces, -Lo is an invalid string is Lo<0

  23. Back to code • Cursor c = myDatabase.rawQuery(…); • String la = latitude; • String lo = longitude; • String ex = “abs(lat – la) + abs(long – lo)”; • String Q = “SELECT * FROM things WHERE ” + ex + “ IN ( SELECT min( “ + ex + “) FROM things) ; “; • Cursor c = myDatabase.rawQuery(Q, []);

  24. File name • String Q = “SELECT filename FROM things WHERE ” + ex + “ IN ( SELECT min( “ + ex + “) FROM things) ; “; • Cursor c = myDatabase.rawQuery(Q, []); • String filename = c.getString(0); • Log.d(“SQLPlay”,”filename:”+filename); • Return filename;

  25. Try it Location location = locationManager.getLastKnownLocation(provider); Random generator = new Random(); int random1 = generator.nextInt( 1000000 ); int random2 = generator.nextInt( 1000000 ); int latitude = (int)(location.getLatitude()*1E6+random1); int longitude = (int)(location.getLongitude()*1E6+random2); • in getFilename function String la = latitude; String lo = longitude; String ex = “abs(lat – la) + abs(long – lo)”; String Q = “SELECT filename FROM things WHERE ” + ex + “ IN ( SELECT min( “ + ex + “) FROM things) ; “; Cursor c = myDatabase.rawQuery(Q, []); String filename = c.getString(0); Log.d(“SQLPlay”,”filename:”+filename); return filename;

  26. finally • In play, paste code to play audio from previous lecture

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